.wrap
{
    width:100%;
    position: relative;
    overflow: hidden;
    &:hover>.btn
    {
        display:block;
    }
    .group
    {
        position:relative;
        height:520px;
        .item
        {
            height:100%;
            position:absolute;
            top:0;
            img
            {
                width:100%;
                height:100%;
            }
        }
    }
    .btn
    {
        width:100px;
        height:100px;
        display: inline-block;
        background: rgba(0,0,0,0.5);
        color:#fff;
        font-size:30px;
        position:absolute;
        top:50%;
        margin-top: -50px;
        line-height: 100px;
        text-align:center;
        display:none;
        cursor: pointer;
        &.prev
        {
            left:50px;
        }
        &.next
        {
            right:50px;
        }
    }
}